import utime
import ustruct
class PCA9685:
	def __init__(self, i2c, address=0x40):
		self.i2c = i2c
		self.address = address
		self.reset()
	def _write(self, address, value):
		self.i2c.writeto_mem(self.address, address, bytearray([value]))
	def _read(self, address):
		return self.i2c.readfrom_mem(self.address, address, 1)[0]
	def reset(self):
		self._write(0x00, 0x00)
	def freq(self, freq=None):
		if freq is None:
			return int(25000000.0 / 4096 / (self._read(0xfe) - 0.5))
		prescale = int(25000000.0 / 4096.0 / freq + 0.5)
		old_mode = self._read(0x00)
		self._write(0x00, (old_mode & 0x7F) | 0x10)
		self._write(0xfe, prescale)
		self._write(0x00, old_mode)
		utime.sleep_us(5)
		self._write(0x00, old_mode | 0xa1)
	def pwm(self, index, on=None, off=None):
		if on is None or off is None:
			data = self.i2c.readfrom_mem(self.address, 0x06 + 4 * index, 4)
			return ustruct.unpack('<HH', data)
		data = ustruct.pack('<HH', on, off)
		self.i2c.writeto_mem(self.address, 0x06 + 4 * index,  data)
	def duty(self, index, value=None, invert=False):
		if value is None:
			pwm = self.pwm(index)
			if pwm == (0, 4096):
				value = 0
			elif pwm == (4096, 0):
				value = 4095
			value = pwm[1]
			if invert:
				value = 4095 - value
			return value
		if not 0 <= value <= 4095:
			raise ValueError("Out of range")
		if invert:
			value = 4095 - value
		if value == 0:
			self.pwm(index, 0, 4096)
		elif value == 4095:
			self.pwm(index, 4096, 0)
		else:
			self.pwm(index, 0, value)
